Fertilizers and their uses.
What are fertilizers?
Fertilizers are basically food for plants. They contain various mixtures that help to ensure that the plant has everything it needs nutrient wise to fulfill its needs.
What do all the numbers mean?
The three numbers that you see on the bag of fertilizer relate to 3 of the 6 macronutrients, nitrogen, phosphorus and potassium. The other three are carbon, hydrogen and oxygen, found in the air and water.
Nitrogen is predominately needed to keep plants green, it has a very important role in the production of chlorophyll, which is responsible for converting sunlight to energy. Nitrogen is needed in large numbers by specific types of plants, namely lawn, evergreens, non flowering trees, leafy shrubs and perennials. Even plants that flower need some nitrogen, and it is always an important part of the plants diet. Nitrogen can be quick or slow release and as a result, certain forms of nitrogen have to be used carefully to avoid burning.
Phosphorus is a compound that has many jobs in the diet of plants. Not only does it encourage root development, fruiting and flowering, but it is also involved in the development of the maturity of the plant, aides in the storage and transfer of energy and helps to metabolise proteins and carbohydrates. For the most part, phosphorus is important to every type of plant, but more so to plants that have a lot of fruiting and/or flowering, and plants that have recently been planted or moved. Phosphorus is quite slow release and is often deficient in many soils. Phosphorus that is not used will not leech very quickly through the soil and is usually maintained in the soil base for the future.
Potassium is actually very important to plants for many reasons. It helps to produce lignin and cellulose, which are key in cell development, influences water intake through the roots, aids in photosynthesis and is responsible for increasing disease and insect resistance. To put it in simple terms, it fortifies the plants and is integral in overall plant health and vigour.
What else do fertilizers have?
Most fertilizers will also have secondary nutrients and micronutrients. Secondary nutrients are needed in moderate amounts and are not going to limit crop growth if there is a deficiency as much as if there is a primary nutrient deficiency. These secondary nutrients would include calcium, magnesium, and sulphur. Micronutrients are also every bit important as primary and secondary nutrients, however, they are not needed in as much volume as the others. Micronutrients are zinc, manganese, boron, copper, molybdenum, chloride, iron and nickel. These are all important in small amounts and are often replaced by adding manures and other composts that are rich in micronutrients. They are also often found in many types of fertilizers, as well as available on their own, for specialized applications.
Should I use organic fertilizers only?
This is a question only you can truly answer. Most fertilizers available on the market today are actually an organic based fertilizer, such as Scotts Turfbuilderã. This means that they are
comprised of at least 65% organic material, and the remaining material that is not organic is chemically derived. This does not mean that they are toxic, or a pesticide. This just means that they are derived from a chemical solution. Many organic based fertilizers are as safe to use as organic fertilizers.
The largest concern about fertilizers is often whether they contain pesticides, and some still do. These products would be limited to fertilizers with weed killers. Fertilizers containing insecticides have been banned from production in Canada for the last 2 years. Organic fertilizers work well, and often have the same secondary and micronutrient availability as organic based or purely chemical fertilizers. Organic fertilizers do not have the same amount of primary nutrients as organic based or chemical fertilizers. In many cases the organic choice is excellent and not much more expensive than the other choices. Organic based fertilizers are also quite good and have an excellent amount of primary nutrients. The choice of which to use is a personal choice, based on environmental and personal health concerns. Many of the older fertilizers are no longer marketed as a retail fertilizer because the demand for them has been replaced by the demand for more organic options.
What does slow release mean?
When you buy a fertilizer that is slow release it is referring to the nitrogen in the product. The phosphorus and potassium in the fertilizer is by nature slow release. The options of slow release are not always the same. Some fertilizers have a 45day slow release “scu” which means the nitrogen source is urea, that is coated in sulphur, and is slowly released over 6 weeks. Other fertilizers may be slowly released over 100 or 120 days, or even longer. These are often a type of polymer coating that slowly dissolves over a given period of time releasing the fertilizer to the soil as it does so.
Can I just use one fertilizer for everything and still get the same results?
No. Fertilizers are tailor made for specific uses for a reason. Established lawns in the spring have a need for more nitrogen, where in the fall they need higher amount of potassium. Fruit trees and vegetables need more phosphorus and potassium, where newly planted plants need more phosphorus. Here are examples of some fertilizers and their usage.
General Purpose Lawn Fertilizer
7-7-7 8kg 20-0-5 (CIL Golfgreen)
8-8-8 8 kg (CIL Vegetable Grower) 32-0-4 (Scotts Turfbuilder Pro)
16-16-16 or 18-18-18 25kg (Synagri) 12-0-18 (CIL Fall Fertilizer)
Tree Fertilizer 20-0-8 9kg, 18kg (Sylvite)
11-0-6 9kg, 18kg (Sylvite)
9-0-14 9kg (Sylvite)
18-4-6 8kg (CIL Tree Food) 10-20-5 (CIL Turfstarter)
Vegetables and fruit
6-12-12 (Tomato Fertilizer w/ extra calcium) Starter Fertilizer
4-6-8 (Green Earth Oganic Vegetable Fertilizer) 5-15-5 (Liquid)
4-10-0 (Bonemeal) 4-10-0 (Bonemeal)
12-0-0 (Bloodmeal) 10-20-5 CIL or 20-27-5 Scotts
7-7-0 Bone & Bloodmeal 6-20-22 25kg Synagri
Which is better, granular fertilizer, liquid fertilizer or water soluble fertilizer?
While there isn’t a better fertilizer, there are more suitable fertilizers for certain applications. Granular fertilizers feed over a protracted period of time, so they last longer in the soils. This means that they can keep feeding the plant longer, which allows for a better uptake of nutrients, as well as a more controlled release of nutrients. Liquids and water soluble fertilizers are usually a quicker release fertilizer, and as such, have to be used more often, causing the plant to go through a growth and crash phase, which can be quite stressful on the plant. Not only that, but you do have to do it more often, which many people do not.
I would use water soluble fertilizers on my annuals and some perennials to give them a constant quick feed boost, and use it regularly, like every 7 to 10 days. Granular fertilizers are excellent for your lawn, trees, vegetables and shrubs as they feed over a longer period of time and do not stress the plant as much by quickly boosting it.
In addition to this, when you look at the numbers on fertilizer, it can be deceiving. When you use a 20-20-20 fertilizer, it is not that formulation once you mix it with water. When you mix the 20-20-20 with water you end up with a 1 litre solution that has .1-.1-.1 composition.
This means you have to use a lot more water soluble fertilizer more frequently to get the same fertilizing results that you do from granular fertilizers.